why are trolls still a problem in this game?

i never understood the philosophy of "verbal abusers/harassers are more toxic to the game than a feeder or troll and takes priority to punish" there is a mute button. hell there is even the ability to completely hide your chat screen. but a troll and intentional feeder cant be stopped or avoided. why are they not punished more harshly and swiftly? there isnt even an option to report something like a tahm kench eating you at your jg and then flashing over a wall or into enemy team.